Method for purification

ABSTRACT

This invention relates to a process for purifying 1,1,2trifluoro-2-chloroethyl difluoromethyl ether (CHF2OCF2CHFCl), and specifically to the separation of chloroform (CHCl3) from an azeotropic mixture of CHF2OCF2CHFCl and CHCl3 which is formed during the production of the ether. According to the invention, the azeotropic mixture is reacted with an alkali metal basic solution in the presence of a water soluble alcohol and refluxed sufficiently to destroy all of the CHCl3. The CHF2OCF2HFCl can then be purified simply and economically by conventional fractional distillation techniques.

United States Patent [19.]

Terrell [451 Jan. 21, 1975 METHOD FOR PURIFICATION [75] Inventor: RossC. Terrell, Plainfield, NJ.

[73] Assignee: Airco, Inc., New York, N.Y.

[22] Filed: Nov. 1, 1972 [21] Appl. No.: 302,987

[52] US. Cl. 260/616 [51] Int. Cl. C07c 41/12 [58] Field of Search260/614 F, 616, 615 A [56] References Cited UNITED STATES PATENTS 9/1970Terrell 260/6l4 F Primary Examiner-Howard T. Mars Attorney, Agent, orFirm-Roger M. Rathbun; Edmund W. Bopp; H. Hume Mathews [57] ABSTRACTThis invention relates to a process for purifying1,1,2-trifluoro-2-chloroethyl difluoromethyl ether (CHF OCF CHFCl), andspecifically to the separation of chloroform (CHCl from an azcotropicmixture of CHF OCF CHFCI and CHCI which is formed during the productionof the ether. According to the invention, the azeotropic mixture isreacted with an alkali metal basic solution in the presence of a watersoluble alcohol and refluxed sufficiently to destroy all of the CHCl TheCHF OCF HFCl can then be purified simply and economically byconventional fractional distillation techniques.

7 Claims, N0 Drawings METHOD FOR PURIFICATION This invention relates tothe purification of l,2,2-trifluoro-2-chloroethyl difluoromethyl ether(CHF OCF CHFCI). While, for commercial development applications, it isdesirable to obtain CHF OCF CHFCI which is at least 99.9% pure, it hasbeen found that in the production of CHF OCF CHFCl by the fluorinationof the corresponding dichloromethyl ether using fluorinating agents inthe presence of pentavalent antimony salts and tetravalent halides asfluorination catalysts, as disclosed in US. Pat. No. 3,527,813,chloroform (CHCL is unavoidably formed as an impurity. Since thischloroform and CHF OCF CHFCl form an azeotropic mixture having a boilingpoint of 53C., which is close to that of pure CHF OCF CHFCl (b.p. 57C.),it has been found to be impractical and uneconomical to remove the CHClcompletely by distillation. Although the CHCl can be removed from thebulk of the product by distillation, the lower boiling fractionscontaining CHCl also contain a substantial amount of CHF OCF CHFCI.

The present invention relates to a simple and economical process for thepurification of CHF OCF CHFCL and specifically to the separation of CHClfrom the azeotropic mixture of CHF OCF CHFCI and CHCl which is formedduring the production of the ether.

In accordance with this invention, it has been found that CHCl can beremoved from the azeotropic mixture of CHF OCF CHCI and CHCl by reactingthe mixture with an alkali metal basic solution, preferably a hydroxidesolution, in the presence of a water soluble alcohol, refluxingsufficiently to destroy all of the CHCL and fractionally distilling torecover pure CHF OCF CHFCL The CHF OCF CHFCl-containing azeotropicmixture, which may contain from about 0.5 to 30% by weight of CHCl isreacted at about 30 to 100C., preferably about 50 to 60C., atatmospheric pressure with an alkali metal basic compound, preferably inthe form of an aqueous solution such as an alkali metal hydroxidesolution, e.g. NaOH, KOI-I, LiOH or Ca (OI-[) although other solutions,e.g. NaOCH CH can be used. Commercial grades of NaOH, for example, 50%GP. U.S.P. solutions, are also suitable. The amount of basic solutionused is determined from the amount of CHCl present in the mixture. Atleast 4 moles of the basic compound, e.g. NaOl-l, per mole of CHCl areused. An excess of basic solution, e.g. 4 to moles basic compound permole of CI-ICl can be used, if desired, and this results in a fasterreaction. A water soluble alcohol is also added to the reaction mixtureto improve the reaction. While methanol is preferred, any water solublealcohol, e.g. lower alkanols having 1 to 6 carbon atoms includingethanol, etc. and polyhydroxy compounds including glycols such asethylene glycol, is suitable. The alcohol is added in an amount of about0.1 to 2 parts by volume, or more, per volume of basic solution used,but is preferably in the range of 0.5 to 1 parts volume of alcohol perpart of basic solution. This mixture is then refluxed until all of theCHCl has been destroyed by reaction. Following refluxing,chloroform-free CHF OCF CI-IFCl can be obtained by fractionaldistillation of the reaction mixture.

The following examples are given to further illustrate the invention,but it is to be understood that the invention is not to be limited inany way by the details described therein.

EXAMPLE I Azeotropic mixtures of CHF OCF CH FC] and CHCI produced duringthe preparation of CH F OCF CHFCI and containing from 0.5 to 35%chloroform are reacted with enough of 50% NaOH solution so that themolar ratio of NaOH/CHCI is equal to about 8 (twice the calculatedquantity). The reaction in each instance is enhanced by adding a volumeof methanol equal to the volume of NaOH solution. The reaction iscarried out in a reactor with a reflux condenser at 50 to C. and apressure of 760 mm. The reaction is completed by re fluxing in the samereactor until all of the CHCI is destroyed and the CHF OCF CHFCI isseparated by fractional distillation. Recovery of CH F OCF CHFCl (99.9%pure) is of the theoretical amount.

EXAMPLES ll THROUGH IV The CHF OCH CHFCI is purified following the sameprocedure described in Example I except that the alkali metal basicsolution used in the reaction is KOH, LiOH and Ca(OH) respectively.

EXAMPLES v THROUGH VII The CHF OCF CHFCI is purified following the sameprocedure described in Example I except that the water soluble alcoholused in the reaction is ethanol, propai101 and ethylene glycol,respectively.

It is claimed:

1. A process for recovering pure l,l,2-trifluoro-2- chloroethyldifluromethyl ether from a reaction product containing an azeotropicmixture of CHF OCF CHFCI and CHCl comprising reacting the productcontaining the azeotropic mixture with an aqueous solution of a basiccompound selected from the group consisting of alkali metal hydroxidesand Ca- (OH) in the presence of a water soluble alcohol selected fromthe group consisting of lower alkanols of l to 6 carbon atoms andethylene glycol, said basic compound being used in an amount of at leastfour moles basic compound per mole of CHCI said alcohol being used in anamount in excess of about 0.1 parts by volume per volume of aqueoussolution, refluxing the reaction mixture sufficiently to destroy the CllCl and recovering essentially pure CHF OCF CHFCI from the reactionmixture by fractional distillation.

2. The process of claim 1 in which the basic compound is an alkali metalhydroxide.

3. The process of claim 2 in which the water soluble alcohol is ethyleneglycol.

4. The process of claim 1 in which the alcohol is present in an amountof 0.1 to 2 parts volume per part volume of basic compound. a

5. The process of claim 4 in which from about 4 to 10 moles basiccompound per mole of chloroform are used.

6. The process of claim 5 in which the basic compound is an alkali metalhydroxide and the alcohol is a lower alkanol.

7. The process of claim 6 in which the alkali metal hydroxide is sodiumhydroxide and the lower alkanol is methanol.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,862,242

DATED 1 January 21, 1975 |NVENTOR(S) ROSS C. TERRELL It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 1, line 2, "1,2,2" should read 1,1,2

line 30, "cfiF ocF cncl" should read CHF OCF CHFCl Signed and sealedthis 6th day of May 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting OfficerI and Trademarks

2. The process of claim 1 in which the basic compound is an alkali metalhydroxide.
 3. The process of claim 2 in which the water soluble alcoholis ethylene glycol.
 4. The process of claim 1 in which the alcohol ispresent in an amount of 0.1 to 2 parts volume per part volume of basiccompound.
 5. The process of claim 4 in which from about 4 to 10 molesbasic compound per mole of chloroform are used.
 6. The process of claim5 in which the basic compound is an alkali metAl hydroxide and thealcohol is a lower alkanol.
 7. The process of claim 6 in which thealkali metal hydroxide is sodium hydroxide and the lower alkanol ismethanol.